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SubjectRe: [PATCH v5 1/2] rpmsg: core: add API to get message length
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Hi Arnaud,

On 8/28/19 10:19 AM, Arnaud Pouliquen wrote:
> Return the rpmsg buffer size for sending message, so rpmsg users
> can split a long message in several sub rpmsg buffers.

Thanks for the patch, I also have a need for the same to be able to
compute permissible payload size. Minor comments below.

>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
> ---
> V4 to V5 :
> - rename rpmsg_get_buf_payload_size to rpmsg_get_mtu
>
> drivers/rpmsg/rpmsg_core.c | 21 +++++++++++++++++++++
> drivers/rpmsg/rpmsg_internal.h | 2 ++
> drivers/rpmsg/virtio_rpmsg_bus.c | 10 ++++++++++
> include/linux/rpmsg.h | 10 ++++++++++
> 4 files changed, 43 insertions(+)
>
> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
> index 8122807db380..daca2e24fc71 100644
> --- a/drivers/rpmsg/rpmsg_core.c
> +++ b/drivers/rpmsg/rpmsg_core.c
> @@ -283,6 +283,27 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
> }
> EXPORT_SYMBOL(rpmsg_trysend_offchannel);
>
> +/**
> + * rpmsg_get_mtu() - get maximum transmission buffer size for sending message.
> + * @ept: the rpmsg endpoint
> + *
> + * This function returns maximum buffer size available for a single message.
> + *
> + * Return: the maximum transmission size on success and an appropriate error
> + * value on failure.
> + */
> +
> +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
> +{
> + if (WARN_ON(!ept))
> + return -EINVAL;
> + if (!ept->ops->get_buf_mtu)

How about calling the ops just get_mtu or rename the function to follow
the ops name, like all the others.

> + return -ENXIO;

Perhaps ENOTSUPP or EOPNOTSUPP.

> +
> + return ept->ops->get_buf_mtu(ept);
> +}
> +EXPORT_SYMBOL(rpmsg_get_mtu);
> +
> /*
> * match an rpmsg channel with a channel info struct.
> * this is used to make sure we're not creating rpmsg devices for channels
> diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
> index 0d791c30b7ea..645c402569ac 100644
> --- a/drivers/rpmsg/rpmsg_internal.h
> +++ b/drivers/rpmsg/rpmsg_internal.h
> @@ -46,6 +46,7 @@ struct rpmsg_device_ops {
> * @trysend: see @rpmsg_trysend(), required
> * @trysendto: see @rpmsg_trysendto(), optional
> * @trysend_offchannel: see @rpmsg_trysend_offchannel(), optional
> + * @get_buf_payload_size: see @rpmsg_get_buf_payload_size(), optional

Missed updating the kerneldoc to the new name.

> *
> * Indirection table for the operations that a rpmsg backend should implement.
> * In addition to @destroy_ept, the backend must at least implement @send and
> @@ -65,6 +66,7 @@ struct rpmsg_endpoint_ops {
> void *data, int len);
> __poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
> poll_table *wait);
> + ssize_t (*get_buf_mtu)(struct rpmsg_endpoint *ept);
> };
>
> int rpmsg_register_device(struct rpmsg_device *rpdev);
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index e757f0038a1c..f80b1ad23e7e 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -178,6 +178,7 @@ static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
> int len, u32 dst);
> static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
> u32 dst, void *data, int len);
> +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept);

Minor nit, virtio_rpmsg_ prefix similar to all the other ops.

regards
Suman

>
> static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> .destroy_ept = virtio_rpmsg_destroy_ept,
> @@ -187,6 +188,7 @@ static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> .trysend = virtio_rpmsg_trysend,
> .trysendto = virtio_rpmsg_trysendto,
> .trysend_offchannel = virtio_rpmsg_trysend_offchannel,
> + .get_buf_mtu = virtio_get_buf_mtu,
> };
>
> /**
> @@ -702,6 +704,14 @@ static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
> return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
> }
>
> +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept)
> +{
> + struct rpmsg_device *rpdev = ept->rpdev;
> + struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
> +
> + return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
> +}
> +
> static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
> struct rpmsg_hdr *msg, unsigned int len)
> {
> diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
> index 9fe156d1c018..9d638bf2bdce 100644
> --- a/include/linux/rpmsg.h
> +++ b/include/linux/rpmsg.h
> @@ -135,6 +135,8 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
> __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
> poll_table *wait);
>
> +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept);
> +
> #else
>
> static inline int register_rpmsg_device(struct rpmsg_device *dev)
> @@ -242,6 +244,14 @@ static inline __poll_t rpmsg_poll(struct rpmsg_endpoint *ept,
> return 0;
> }
>
> +static ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
> +{
> + /* This shouldn't be possible */
> + WARN_ON(1);
> +
> + return -ENXIO;
> +}
> +
> #endif /* IS_ENABLED(CONFIG_RPMSG) */
>
> /* use a macro to avoid include chaining to get THIS_MODULE */
>

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